Presently, the well-known navigation system necessitates a user to specify a destination in a pinpoint manner. That is, the user needs to specify a destination by locating an intended point on a map displayed on a display unit, selecting an address or a facility from a menu, or specifying a place stored in memory.
However, it may often occur that a user does not conceive of a specific visit place but is sure of conditions for a place to visit. For this purpose, there is available a navigation system that allows a user to supply conditions for a place to visit and retrieves and proposes visit places satisfying the conditions.
For example, the technology described in Patent document 1 below allows a user to supply a distance to the destination, the time required to reach the destination, and the like prior to initiation of the route guidance. The technology displays a list of places matching the conditions and allows the user to select an intended place from the list to determine the final destination.
The technology described in Patent document 2 below allows a user to supply an area the user wants to visit, a travel period, an estimated travel expense, and the like prior to initiation of the route guidance. The technology determines a facility satisfying the conditions as a destination.
Patent document 1: JP-2004-132884 A
Patent document 2: JP-2004-340757 A
Generally, a user often conceives of specific visit places when the destination is a nearby place. When the destination is faraway, however, it may often occur that the user does not conceive of specific visit places or the sequence of places to visit (visit sequence) and determines visit places or the visit sequence as the user approaches the destination. For example, a user intends to go on a drive from his or her home in Nagoya City and provisionally determines to just got to the Kansai area (including Kyoto City, Osaka City, Nara City, and Kobe City); when approaching Kyoto City via Nagoya-Kobe Expressway after the departure, the user finally determines to visit a certain temple in Kyoto City and then a certain shrine in Nara City.
When a visit place is indefinite at the departure time, a general navigation system cannot start the route guidance from the departure time. According to the above-mentioned technology described in Patent document 1 or 2, the departure time eventually determines a specific visit place. The user cannot determine only a destination area at the departure time or determine a specific visit place or a visit sequence halfway through the route. When the user determines a visit place or a visit sequence halfway through the route, additional operations are needed to change the already determined destination.
However, it is difficult for the general navigation system to change the visit place or the visit sequence in process of the route guidance. This is because many navigation systems are designed not to accept fine-tuning operations while a vehicle is running. First of all, the systems do not consider that the visit place or the visit sequence is surely changed.